514 y. G. CLAPP GLACIAL PERIOD IN NEW ENGLAND 



giaciation (see page 524), and the fact, recorded elsewhere, that a marked 

 continental elevation took place in pre-Kansan time indicates that some 

 of the valleys probably date back to the close of the Tertiary period. 



OLD TILLS 



General statement. — In the year 1905 certain deposits of till in Brock- 

 ton and Stoughton, Massachusetts, were described.* The deposits were 

 foimd in excavations underneath the ordinary surface till of the region, 

 were very different in character from the surface till, and were definitely 

 assigned to Kansan or pre-Kansan age. 



In 1899 Stone described se\eral feet of a "hard, tough clayey till that 

 resisted erosion wonderfully, and broke up into blocks 2 or 3 feet in diam- 

 eter" on Penobscot river, at the mouth of South Twin lake, in central 

 Maine, f "Above this was a lighter-colored and less compact till forming 

 a north-south ridge or elevated drumlin." Stone discussed the possibility 

 of the lower of these two deposits being an old till, but for some reason 

 decided that it was only a phase of the Wisconsin. 



With these two exceptions, no descriptions of old tills in jSTew England 

 are known to have been published. The present writer has not seen these, 

 but has noted a number of similar exposures of till which can hardly be 

 explained except on the supposition that they are very old. 



Exposure at South Norridgewock, Maine. — On the road leading down 

 to Kennebec river from the village of South Norridgewock there is an 

 8-foot section of "old-looking". till, oxidized very yellow and brown from 

 top to bottom. For a foot or two at the top the material is ordinary 

 till composed of moderately fresh and polished pebbles, mostly of foreign 

 origin. Tlie rest of the section is nearly as hard as rock, standing per- 

 pendicular and being very firm and tough. It consists largely of pebbles 

 less than a foot in diameter, and most of the fragments are dark sandy 

 slate, but some are quartzite. Many are angular, but some are well 

 rounded. A few are striated. The till is very clayey and the clay sticks 

 firmly to the pebbles. The mass is somewhat iron-stained and the iron 

 takes some part in the process of cementing. So far as could be deter- 

 mined from a brief examination, the deposit does not contain any granite 

 pebbles. The relation to other deposits than the superficial till could not 

 be determined. 



Section at South Lawrence, Massachusetts. — A cut exposed in 1906 

 along the Boston and Maine railroad at South Lawrence, Massachusetts, 

 showed the section illustrated in figure 2. 



• M. L. FuHer : Journal of Geology, vol. ix, pp. 3'll-329. 

 • t Monograph no. 34, U. S. Geological Survey, p. 285, 



